1. Field of the Invention
The present invention relates to a shielding system for microwave ovens. It is well known in the art of microwave ovens the need of providing shielding systems, particularly in connection with glass in the oven door, which shall allow the user to look into the cooking cavity of the oven without any leakage of microwaves through the transparent door.
2. Description of the Related Art
There are also other uses of microwave shielding systems, particularly for microwave ovens having an electromagnetic induction coil provided outside the cooking cavity, adjacent the bottom wall thereof. Such an oven is disclosed by EP-A-464390. In this type of ovens the shielding system must act as a reflective boundary for microwaves (typically in the range of 2.45 GHz) and be substantially “transparent” to the electromagnetic waves (typically about 20 to 30 kHz) responsible for induction heating. Moreover, large losses in the shielding system due to eddy current loss in the surface portion of the shielding system is preferably avoided. In the above application the use of a non-magnetic metal mesh within a predetermined size range as microwave shielding system solved the above technical problem.
This known system is not completely satisfactory from an energy loss point of view. As a matter of fact the mesh is heated both by microwave absorption and by electromagnetic induction. In a connected mesh, microwave losses can be rather substantial due to the fact that it is possible to have a multitude of different resonant pathways in the connected mesh. Such heating causes a deformation and therefore such deformation has to be absorbed by one or more insulating layers on which the mesh is placed.